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Aerodynamic performance of an un-located high-pressure turbine rotor

Part of: ISABE 2017

Published online by Cambridge University Press:  13 July 2017

L. Pawsey ,
D. J. Rajendran  and
V. Pachidis
L. Pawsey*
Affiliation:
Centre for Propulsion Engineering, School of Aerospace, Transport and Manufacturing, Cranfield University, Bedford, UK
D. J. Rajendran
Affiliation:
Centre for Propulsion Engineering, School of Aerospace, Transport and Manufacturing, Cranfield University, Bedford, UK
V. Pachidis
Affiliation:
Centre for Propulsion Engineering, School of Aerospace, Transport and Manufacturing, Cranfield University, Bedford, UK
*
[email protected]; [email protected]
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Abstract

The rotor sub-assembly of the high-pressure turbine of a modern turbofan engine is typically free to move downstream because of the force imbalance acting on the disc and blades following an un-located shaft failure. This downstream movement results in a change in the geometry of the rotor blade, tip seals and rim/platform seals because of the interaction of the rotor sub-assembly with the downstream vane sub-assembly. Additionally, there is a change in the leakage flow properties, which mix with the main flow because of the change in engine behaviour and secondary air system dynamics. In the present work, the changes in geometry following the downstream movement of the turbine, are obtained from a validated friction model and structural LS-DYNA simulations. Changes in leakage flow properties are obtained from a transient network source-sink secondary air system model. Three-dimensional Reynolds-averaged Navier-Stokes simulations are used to evaluate the aerodynamic effect from the inclusion of the leakage flows, tipseal domains, and downstream movement of the rotor for three displacement configurations (i.e. 0, 10 and 15 mm) with appropriate changes in geometry and leakage flow conditions. It is observed from the results that there is a significant reduction in the expansion ratio, torque and power produced by the turbine with the downstream movement of the rotor because of changes in the flow behaviour for the different configurations. These changes in turbine performance parameters are necessary to accurately predict the terminal speed of the rotor using an engine thermodynamic model. Further, it is to be noted that such reductions in turbine rotor torque will result in a reduction of the terminal speed attained by the rotor during an un-located shaft failure. Therefore the terminal speed of the rotor can be controlled by introducing design features that will result in the rapid rearward displacement of the turbine rotor.

Keywords

Shaft failureaxial turbineCFDun-locatedrim sealtip sealturbine overspeed
Type
Research Article
Information
The Aeronautical Journal , Volume 121 , Special Issue 1242: The International Society of Air-breathing Engines (ISABE) 2017 Conference Special Issue , August 2017 , pp. 1200 - 1215
Copyright
Copyright © Royal Aeronautical Society 2017 

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Footnotes

This paper will be presented at the ISABE 2017 Conference, 3-8 September 2017, Manchester, UK.

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